19^ 



which was a Water-level, which had been set on fire about 

 18 months previously by an explosion of carburetted hydrogen 

 gas. " This place was immediately cleared of all the smoke, 

 sulphur, &c., which could not be moved by the power of 

 the cupola ;" thus affording additional evidence of the supe- 

 riority of Mechanical Force over the power of Rarefaction in 

 promoting Ventilation, an increase of which, as the Author 

 observes, would invigorate the pitmen, and enable them to 

 go through their labour with greater comfort ; in many cases 

 with improved health ; and the general working of the mine be 

 greatly facilitated. The present velocity with which wind 

 travels through mines is at the rate of from three to four feet 

 per second. This velocity suits the Safety Lamp, inasmuch 

 as a wind travelling at a greater speed in a highly explosive 

 medium, would cause the flame to pass the gauze of the 

 lamp, and explode the mine. But were the current of air 

 to be increased to double that velocity, there would be no 

 necessity for the Safety Lamp at all." 



In discussing the relative consumption of fuel, and the 

 results to be obtained by his method of Ventilation and 

 that of the plan in general use, Mr. Fourness gives the 

 following calculations in support of his invention being 

 more economical and efficient. 



" I may here state how much fuel would be required 

 for a furnace, either at the top or bottom of the shaft, to 

 exhaust 10,180 cubic feet of air per minute. The answer 

 is 46 cwt. of good coal in 24 hours, or rather better than 

 4i lbs. of coal per minute; according to the rules for 

 ascertaining the quantity of fuel required for an ordinary 

 mine, say the depth of upcast 200 yards, as the length of 

 shaft is not of so great importance for ventilation, when 

 reaching above 60 or 70 yards ; making a difference of 

 21 lbs. of coal per minute, or 36 cwt. per 24 hours, for it 

 appears plain that 10 cwt. of good coal, (where mechanical 



